AOL's Bunko Patrol at work: Devices that promise to save you money and gas are hawked everywhere.

With gas prices above $3.50 a gallon, companies which manufacture "fuel saving" devices are thriving. These companies are vying for the motoring public's dollars and preying on their ignorance.

Whenever the price of gas goes up, I receive hundreds of e-mail inquiries about such devices. So let's take a close scrutinizing look at some of these "technologies" to see if there's any validity here.

Magnetized products are anything but True North

Such devices wrap around the fuel line just prior to fuel inlet. The claims of increased fuel economy are anywhere from 5% to 20% (usually determined by their customers' testimonies).

Petro-Mag is one of the most popular, and the company claims its product works the same way cholesterol medicine works on your heart: By preventing gasoline from clogging up fuel lines. They claim the fuel activator lasts for the life of the engine.

Sounds pretty impressive, huh? But the Environmental Protection Agency says it doesn't work. They tested several products, like Petro-Mizer, Polarion-X, Super-Mag Fuel Extender, Wickliff Polarizer and others. There was absolutely no improvement in fuel economy, the EPA says.

Air swirling technology is bunk

Air swirling technology is installed in the air intake just prior to the engine throttle. In theory, it works by creating a small vortex of air, resulting in better atomization of the fuel droplets in the air/fuel mixture, making the combustion process more efficient.

One of the most popular is the Tornado Fuel Saver. That device claims to increase fuel economy from 7% to 28%, and also boasts of increasing horsepower by 4 hp to 13 hp. And they claim it takes 2 to 5 minutes to install.

Vince Ciulla, a nationally noted auto expert, says he's been testing the Tornado for the past three months. He saw increases of .1 mpg, .2 mpg and in one instance, fuel economy dropped by .4 mpg.

"So much for the fuel economy increase," he said.

There was also zero increase in horsepower, even though drivers said their cars felt more powerful. Ciulla hooked the cars up to dynamometers to test the power, and came up empty.

"The feel of increased power is what the consumer expects to feel," he said. "So it is a matter of perception."

PCV "air bleed" technology only bleeds your wallet

Products like the Ram-Jet Fuel Saver claim that by bleeding air into the engine, they break down corrosive particles that could dirty engines, and feed extra air into the engine whenever it's working hard. There are others like ADAKS Vacuum Breaker Air Bleed, Auto-Miser, Ball-Matic Air Bleed, Grancor Air Computer, and Hot Tip.

They've all been tested by the EPA, and found to be useless.

Fuel additives

These companies claim that by adding their product to the fuel tank, you will realize fuel mileage savings. Some claim to increase fuel octane and increase fuel efficiency by making engines burn cleaner. You use them by adding it to the fuel tank before filling up.

The EPA has also tested a bunch of these, like Bycosin, El-5 Fuel Additive, and Dyno-Tab Fuel Booster, and found they do nothing.

There are many other "technologies" out there that claim similar fuel mileage increases. Among them are:

Vapor Bleed Devices: These are similar to the air bleed devices (PCV), except that induced air is bubbled through a container of a water and anti-freeze mixture, usually located in the engine compartment.

Ignition Devices: These devices are attached to the ignition system or are used to replace original equipment or parts.

Fuel Line Heaters: These devices heat the fuel before it enters the fuel delivery system. Usually the fuel is heated by the hot engine coolant or by the exhaust or electrical system.

Metallic Fuel Line Devices: These devices contain several dissimilar metals that are installed in the fuel line and supposedly cause ionization of the fuel (similar in theory to the magnetic fuel saving devices.)

Oils and Oil Additives: These materials are usually poured into the crankcase.

All of these 'fuel-savers' have been tested by the EPA and have been found to be of no benefit to MPG.